The present invention relates to a magnetic-optical disc memory system, and more particularly to a magnetic-optical disc file system which is well suited to stabilize a switching operation that is performed when a header signal and a data signal are detected by separate photodetection means and are switched and synthesized when writing or erasing data in a sector unit.
An example of a magnetic-optical information recording and reproducing system, in which data is written or erased by a thermomagnetic effect and is read out by a magnetooptical effect, has been proposed in `Technical Report of Electronics and Communications Society (in Japan)` CPM 83-53, pp. 13-19. This system employs a recording medium in which data is written with a magnetic signal, while address information is written with a phase signal in the form of embossed pits. As regards a read-out signal detecting system, however, the proposal does not refer to a method of processing both the data and address information items, namely, switching them.
One of the inventors of the present invention has already proposed, with joint inventors who are not the inventors of the present invention, a magnetic-optical disc memory system in which detection means for a header signal and detection means for a data signal are disposed separately from each other and in which outputs of the detection means are added to each other in order to synthesize both the signals. The proposal is described in Japanese Patent Application Laid-open No. 136047 of 1985 (Japanese Patent Application No. 242006 of 1983) and corresponding U.S. Pat. application Ser. No. 685123. This proposal, however, refers to nothing of switching both the signals.